1. Field of the Invention:
The present invention relates to an improvement of a single lens reflex camera having an electro-magnetic device.
2. Description of the Prior Art:
It has been widely known to have an electro-magnetic device linked with various functions of a camera for starting up and controlling each function, and, generally speaking, a power source mounted to a camera is limited to one with small output (low voltage and low current) because of space limitation derived from handling characteristics and portable characteristics of a camera. Therefore, the output of said electro-magnet is necessarily limited. However, a conventional type of electro-magnetic device which has been hereto utilized is of such type as shown in FIG. 1. That is, such device is so composed that a movable iron piece 1 is attracted by the magnetic flux .phi..sub.1 generated by a permanent magnet 4, then the magnetic flux .phi..sub.2 is generated by flowing current to exciting coils 5, 6 for releasing said movable iron piece 1 by said magnetic flux .phi..sub.2. However, in the case of such device, since the magnetic flux .phi..sub.2 generated by the coils 5,6 forms a closed magnetic circuit through the permanent magnet 4 which has very large magnetic reluctance, it can not be so strong. Thus, the current flow to the coils 5, 6 for releasing the magnetic pole planes 1a, 1a' of the movable iron piece 1 from the magnetic pole planes 2a, 2a' of the yokes 2, 2' had to be large in the case of such conventional device.
Therefore, since such conventional electro-magnetic device consumes a large amount of power, the power source voltage is apt to be lowered below the prescribed value. Thus in a camera in which release is performed electro-magnetically, as said electro-magnet becomes active or inactive depending on the degree of droppage in voltage, the electro-magnet can not be completely controlled. Also in a camera in which aperture stop down and shutter control are done by an electro-magnet, control of aperture stop down and of shutter mechanism can not be sufficiently done since its prescribed voltage is lowered and thus appropriate exposure can not be obtained.
An object of the present invention is to eliminate the above mentioned shortcomings and is to provide a single lens reflex camera in which the amount of current required for pulling apart a movable iron piece of an electro-magnetic device, which activates a starting up means of said camera, can be made small for reducing the amount of power consumption.
Another object of the present invention is to conduct the driving control of various functions of a single lens reflex camera by a plural number of electro-magnetic devices, wherein by impressing pulse voltage consecutively on each electro-magnetic device, the sequence control of a camera can be easily made.
Further, another object of the present invention is to make a camera control circuit electronically inactive by the output of an erroneous function prevention circuit which functions when a power source voltage is lowered than a prescribed value and at the same time an indication of warning for said non-active state of the camera control circuit is made.